Fermentation products, such as ethanol, are produced by first degrading starch-containing material into fermentable sugars by liquefaction and saccharification and then converting the sugars directly or indirectly into the desired fermentation product using a fermenting organism. Liquid fermentation products such as ethanol are recovered from the fermented mash (often referred to as “beer” or “beer mash”), e.g., by distillation, which separate the desired fermentation product from other liquids and/or solids. The remaining faction, referred to as “whole stillage”, is dewatered and separated into a solid and a liquid phase, e.g., by centrifugation. The solid phase is referred to as “wet cake” (or “wet grains” or “WDG”) and the liquid phase (supernatant) is referred to as “thin stillage”. Dewatered wet cake is dried to provide “Distillers Dried Grains” (DDG) used as nutrient in animal feed. Thin stillage is typically evaporated to provide condensate and syrup (or “thick stillage”) or may alternatively be recycled directly to the slurry tank as “backset”. Condensate may either be forwarded to a methanator before being discharged or may be recycled to the slurry tank. The syrup consisting mainly of limit dextrins and non-fermentable sugars may be blended into DDG or added to the wet cake before drying to produce DDGS (Distillers Dried Grain with Solubles).
It is known to commercially use the various byproducts and residues derived from the fermentation processes like the ethanol production process. Distillers residues or byproducts, as well as by-products of cereal and other food industry manufacturing, are known to have a certain value as sources of protein and energy for animal feed. Furthermore, the oil from the by-products like DDGS can be recovered as a separate by-product for use in biodiesel production or other biorenewable products are sought.
The by-products like DDG, DDGS or WDG comprises proteins, fibers, fat and unconverted starch. For example DDGS contains typically about 30% of protein. While the protein content is high the amino acid composition is not well suited for monogastric animals if used as animal feed. In general processing of DDGS, especially drying time and temperature are effecting the availability and digestibility of the amino acids, especially lysine.
Furthermore, the by-products are mainly fibrous by-products comprising Crude Fibers (CF), which are structural carbohydrates consisting of cellulose, hemicellulose and indigestible materials like lignin. The structural carbohydrates are not digestible in animal's small intestine. Fibers are characterized and analyzed by different methods and can be divided into crude fibers (CF), neutral detergent fibers (NDF) and acid detergent fibers (ADF). The proportion of cellulose and lignin in the crude fibers fraction also determines the digestibility of crude fibers or its solubility in the intestine. High cellulose and lignin concentrations mean reduced digestibility and vice versa. Hemicelluloses are capable to bind water. The soluble part of fibres the soluble non-starch-polysaccharides (NSP) cannot be digested by monogastric animals like swine and poultry, but increase viscosity, due to their capability to bind water, and are a nutritional constraint, since they can cause moist, sticky droppings and wet litter. The antinutritional effect of soluble NSP's is mainly related to the increase in digesta viscosity. The increased viscosity is slowing down the feed passage rate and hinders the intestinal uptake of nutrients and can lead to decreased feed uptake The viscosity increase a) hinders the intestinal absorption of nutrients and can result in negative effect on the consistency on faces and even symptoms of diarrhea, b) slowing down the feed passage rate and possibly to decreased feed intake. Another effect of NSP's is the so-called “Nutrient Encapsulation”. The NSP's in plant cell wall encapsulated starch, protein, oil and other nutrients within the plant cell which is an impermeable barrier preventing full utilization of the nutrients within the cell.
Furthermore the soluble NSP's are responsible for high viscosities during fermentation and are directly influencing separation and drying conditions of fermentation by-products like DDGS in the production process. The bound or encapsulated water in the product is difficult to remove and causes the use of higher drying temperatures and also longer drying time, adversely affecting the quality of temperature-sensitive products like amino acids. The availability and digestibility of essential amino acids in the by-products are lowered by high temperatures and long drying time during production. Examples for NSPs are arabinoxylans, beta-glucans, galactomannans and alpha-galactosides.
As the by-products are used in animal feed for monogastrics animals like pigs and poultry it is important that the by-products have high concentrations of protein with a good amino acid composition and high availability and low soluble fibers content.
Therefore, the two ways for an improvement of a fermentative production plant ton increase their efficiency and profitability are an improved production process and the improvement of the quality of the by-products.
In the prior art, a lot of specific processes or treatment methods are described to improve fermentative production processes.
For example, WO 2007/056321 A1 discloses a method of dewatering whole stillage comprising adding enzymes to whole stillage in the ethanol production to improve the solid-liquid separation in the process.
WO 02/38786 describes a process of ethanol production, whereby enzymes are used for thinning the liquefied whole grain mash and the thin stillage. Enzymes are applied to the liquefied mash before the fermentation starts as well as to the thin stillage after centrifugation of the whole stillage.
The US 2006/0275882 A1 describes a process for producing a fermentation product wherein the viscosity of the mash is reduced by the application of enzymes before or during the fermentation.
The US 2006/0233864 A1 describes a method for improving the nutritional quality of fibrous by-products for a food manufacturing process, wherein the fibrous by-products like DDGS are inoculated with a filamentous fungus to improve the quality of the by-product.
Some ethanol plants use milo, wheat, or barley in the fermentation process, depending on geographical location and time of the year. As a result, nutrient composition can vary among DDGS sources. Because of the near complete fermentation of starch, the remaining amino acids, fat, minerals and vitamins increase approximately three-fold in concentration compared to levels found in corn. Despite the significant increase in crude protein, the poor amino acid balance of DDGS must be addressed when formulating swine and poultry diets.
Therefore, it is an object of the present disclosure to provide improved methods for improving the quality of the by-products from fermentation processes. It is further a need for methods for further improvement of the process ability by dewatering the stillage and to provide improved methods for increasing the amount of recoverable oil.